There are varied reasons why moisture gets developed in the basement. We need to not only understand the problems but find a solution immediately for the same so that the house does not become uncomfortable and disease prone.
One of the major reasons for moisture in the basement is inadequate grading. If the ground is not leveled, the water from the house reaches the basement and accumulates there, giving problems to the house owners. The solution to get rid of the moisture is placing earth around the house so that water will slope away from the wall. It should be a minimum of 1 Inch per foot for a minimum of 6 feet.
There are defective or missing gutters and downspouts due to bad plumbing during the construction of the house. This causes the rainwater to come inside the dwelling space. You can place at least 1 downspout per 50 linear feet of roof eave. The extension will make sure the water is discharged at least 4 feet away from the boundary.
If you can manage to build sloped concrete sidewalks around the basement then it can prove to be really effective during the rains. There are improperly designed window wells right next to the basement wall. They work like drain for the basement, draining the water toward it rather than away from the foundation. This is mostly due to improper construction.
Develop the window well filled from the footing to the window sill with 3/8th to 3/4th inch coarse aggregate. Make sure that the supplementary drain tile extension is extended from the bottom to the base of the window well.